A hundred pieces by master painter Chang Dai-Chien worth HK$500 million go on show this week, offering a glimpse into the life of not only an exceptional artist but a generous man.

Many of the works by Chang, also known as Zhang Daqian, have never before been publically displayed. They come from the vaults of solicitors John Tong Chor-nam and Herman Tsoi Hak-chiu for an exhibition titled "A Testament of Friendship - Zhang Daqian Paintings and Calligraphy from the Collection of You Yi Tang".

For the past two decades, the solicitors have acquired the works through Shen Weichuang, former editor of the now defunct art magazine Panorama and a close friend of Chang's.

"Zhang was a big spender. He hardly had any savings but when his friends were in need of money, he'd give away his artworks to help out," Tsoi says, recounting the time when Shen's magazine was going through a rough patch in the early 1970s. Born in Sichuan but living in the US, Chang still sent over a landscape painting to comfort his old friend.

Shen treasured the piece, which he titled Evergreen Mountains, and kept it until months before he died in 1995. The splashed-ink-and-colour piece will be one of the works on show at the Convention and Exhibition Centre from October 5 to 8. None of the pieces is up for sale.

Chang was ranked by market database Artprice as last year's best-selling artist at auction, toppling his one-time acquaintance Pablo Picasso from the top spot. But neither Tong nor Tsoi care to profit from their collection, which also includes Chinese masters such as Chao Shao-an, Qi Baishi and Xu Beihong.

The works by modern ink artist Chang include paintings and calligraphic pieces, charting his artistic development from the 1930s to the early 1980s, shortly before his death in 1983 aged 83.

Since they began collecting Chang, Tsoi and Tong's admiration has grown for his artistic versatility, which included forging old Chinese masterpieces.

"Every one of these paintings is different," Tong says. "Zhang was good at portraying ladies and scholars, gongbi technique, splashed-colour … everything."

Tong and Tsoi joked they couldn't afford their own collection if they were to buy it today - Sotheby's estimates the total value of the exhibits to be at least HK$500 million. But they aren't tempted to cash in.

"You can always buy another luxury property, but a great piece of art is irreplaceable," Tong says.

Yet no matter how reluctant they are to part with their collection, one day it will have to go somewhere.

"Zhang once said the museum is the best home for a painting," Tong said. The two lawyers hope to donate the works in the future to a museum that appreciates Chang's art.

This article appeared in the South China Morning Post print edition as Pupil to master: art show charts Chang's career